1. Field of the Invention
The present invention relates to software and, in particular, tolerating faults during the booting of computer software.
2. Background of the Invention
A device driver is a software program that links a peripheral device or internal computer function to the operating system. The device driver contains the precise machine language necessary to activate all device functions and includes detailed knowledge of the device's characteristics, such as the number of keys in a keyboard or the number of pixels of screen resolution of a display. For example, a computer typically includes a keyboard device driver for activating keyboard functions. Device drivers may interface with hardware, the operating system, or other device drivers.
Booting a computer refers to causing a computer to start executing instructions. Generally, computers contain built-in instructions in a read-only-memory (ROM) that are automatically executed at start-up or when the computer is powered on. These set of computer instructions are typically called a bootstrap routine. The bootstrap routine searches for the operating system, loads the operating system and passes control to the operating system. The operating system may search for device drivers and store device driver specific information in predetermined memory locations.
Often, testing and debugging a newly designed device driver is a difficult task. When designing device drivers, as with all software development, bugs or run time errors occur throughout the development process. When an application program has a bug, the worse that can happen is that the operating system must be rebooted (the computer is powered off and back on) to resume operation. Unlike an application program, a bug in a device driver usually crashes the operating system rendering it inoperable and requiring a re-install of the operating system.
There may be many reasons why the device driver caused the operating system to crash. First, the operating system accessing the device driver may have bugs. Second, the device driver may also have bugs causing the operating system to crash.
One method for avoiding an operating system crash involves a manual fix to disable the newly designed device driver. This consists of booting into another operating system and renaming and copying files around on the disk drive. For example, if a computer has multiple operating systems which have access to the same file system which includes the faulty device driver, a user could boot into the operating system which is operable and delete the faulty device driver. While this is faster than re-installing the operating system, it is still a painstaking and time-consuming process. In addition, the user must have a good working knowledge of the operating system and file structure. If a faulty device driver is loaded onto multiple computers in a network, the device driver installed on each computer would have to be deleted. This time spent rebooting the various computers by hand substantially reduces the amount of time available in the software development process required to fix the bug. Likewise, any user of the software containing or using the faulty driver will be unable to use their computer until the operating system is reinstalled and the faulty driver is deleted.
It is therefore desirable to provide a method and article of manufacture, such as a magnetic disk having programmed computer instructions, which enables a computer to withstand an error generated by a faulty device driver and/or faulty operating system. In particular, the method and article of manufacture should prevent the faulty device driver from crashing the operating system. The method and article of manufacture should identify the faulty device driver, disable the device driver and not require time-consuming manual fixes of a single computer or multiple computers on a network.